Many regions of the world have inadequate rainfall to support lawns, gardens and other landscaping during dry periods. Sprinklers are commonly used to distribute water over such landscaping in commercial and residential environments. The water is supplied under pressure from municipal sources, wells and storage reservoirs.
Generally sprinklers fall into several basic categories, including hose end, drip, spray, impact, rotary stream and rotor types. For convenience, reliability and economy, most vegetation around residences, commercial sites, golf courses and playing fields utilize spray, impact and/or rotor type sprinklers which are usually connected to series of underground pipes. Valves are connected to the pipes and are typically opened and closed by a programmable electronic irrigation controller.
Spray type sprinklers are usually only used for watering smaller areas. Rotor type sprinklers pioneered by Edwin J. Hunter of Hunter Industries, Inc. have largely supplanted impact drive sprinklers for watering larger areas, particularly golf courses and playing fields. Rotor type sprinklers are quieter, more reliable and distribute a relatively precise amount of precipitation more uniformly over a more accurately maintained sector size.
Both spray type and rotor type sprinklers employ an extensible riser which pops up out of a fixed outer housing when water pressure is applied. The riser has a nozzle from which water is distributed. In rotor type sprinklers the nozzle is located in a rotating head or turret mounted at the upper end of the riser. The tiny orifices in spray type sprinkler nozzles are highly susceptible to clogging by dirt and other debris. The riser of a rotor type sprinkler incorporates a turbine which drives the rotating head via a gear train reduction, reversing mechanism and arc adjustment mechanism. Rotor type sprinklers used on golf courses sometimes include an ON/OFF diaphragm valve in the base thereof which is pneumatically or electrically controlled. The diaphragm valves and turbines of rotor type sprinklers are highly susceptible to damage by dirt and other debris.
Irrigation riser assemblies, either gear driven or spray, require some means of fixing the rotational position of the riser relative to the outer sprinkler housing within which the riser telescopes. If the spray pattern is a part circle or the spray pattern is oriented to the landscape in some manner the riser also needs some means for permitting the relative rotational position of the riser relative to the outer housing. The conventional way of accomplishing this result requires a complex and expensive cooperating rib structure as disclosed in U.S. Pat. No. 4,220,283. Typically a second part is required to interface with the ribs formed on the inner wall of the outer housing. Those sprinkler designs that do not use a second part use a solid ring with teeth that is part of the riser and which interfaces with the ribs formed on the inner wall of the outer housing. These molded teeth have a short life because they are solid and relatively inflexible and therefore tend to break and/or abrade over time, dependent upon the amount of manual rotation of the riser relative to the outer housing.
It has heretofore been common to include mesh screens or strainers at the lower inlet ends of both spray type and rotor type sprinklers to avoid clogging and damage to critical components otherwise afflicted by dirt and other debris carried in the water supply. However, any strainer in an irrigation sprinkler can itself become clogged or covered with debris in the form or organic and/or inorganic matter. The flow of water can become so impaired in a spray type sprinkler that the riser will not extend. In a rotor type sprinkler the flow of water can become so impaired that the turbine will not properly drive the nozzle through its rotational arc. The required degree of filtering of the incoming water is not always the same for the nozzle as the mechanical drive components of a rotor type sprinkler. A rotor type of sprinkler has a relatively large nozzle but its stator jets, for example, may be very susceptible to particle clogging. A fine mesh debris strainer may not be needed in a particular flow path within a rotor type sprinkler and may impose excessive flow resistance that can limit the reach of the rotor's water stream.